Rock bit having cuttings channels for flow optimization

ABSTRACT

A rock bit for blast hole drilling includes a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side and a ported boss, and a plurality of roller cones. Each roller cone is secured to the respective bearing shaft for rotation relative thereto. A row of crushers is mounted around each roller cone. Each leading side and each trailing side are recessed relative to the respective shirttail. Each side has a cuttings channel formed therein. The rock bit further having a nozzle disposed at each ported boss. wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle.

FIELD OF INVENTION

The present invention relates to a rock drill bit having a body including a plurality of legs with each leg supporting a roller cone and having a ported boss formed with a nozzle for dispensing a fluid to facilitate evacuation of cuttings.

BACKGROUND ART

Rotary drills have emerged as an effective tool for specific drilling operations such as the creation of blast holes and geothermal wells. The drill typically comprises a rotary drill bit having three journal legs that mount respective cone-shaped rolling cutters via bearing assemblies that include rollers and balls.

Typically, the drill bit is attached to one end of a drill string that is driven into the borehole via a rig. The cutting action is achieved by generating axial feed and rotational drive forces that are transmitted to the drill bit via the drill rods coupled end-to-end. Each of the cone-shaped cutters comprise externally mounted hardened cutting buttons positioned at different axial regions for optimised cutting as the drill bit rotates and weight is applied. Accordingly, the rock formation beneath the bit is crushed as the bit is rotated and moves through a formation. The cuttings created by the drilling operation are formed from fine particles which are highly abrasive. To remove these fines from the cutting zone within the bore hole a drilling, such as air or drill mud, is supplied to the drill bit from the surface through the hollow drill string. The cuttings are carried to the surface suspended in the drilling fluid. As will be appreciated, grinding and re-grinding of cuttings reduces the penetration rate of the bit and shortens the bit lifetime.

Conventionally, the drilling fluid, typically air, is directed by nozzles against the cutter cones to wash away the cuttings. However, the drilling fluid jets can trap the cuttings at the bottom of the hole or at regions of the bit with the result that the cuttings are re-ground to an abrasive powder before evacuation. Example rotating bits and cutters are described in U.S. Pat. Nos. 6,450,270; 9,260,922; 4,513,829, 7,059,430, 4,848,476; 8,079,427 and 7,302,374.

In particular, U.S. Pat. No. 9,260,922 discloses an earth boring drill bit having an alternate path to allow cuttings to be ejected or evacuated from the drill bit and up the bore hole. The evacuation hole allows larger sized cuttings to evacuate from the bit without having to be continually ground by the cutters until the cuttings are small enough to follow a path around the edge of the shirttail of the bit and up the borehole. A cuttings restrictor is disposed at the inlet of the evacuation hole. The cuttings restrictor ensures that only cuttings that are sized to move completely through the evacuation hole and exit the drill bit are allowed to enter the evacuation hole.

Accordingly, existing drill bits are disadvantageous in that in certain instances cut material is not ejected or evacuated sufficiently from the region of cutting creating which in turn reduces cutting efficiency and leads to accelerated wear problems. Additionally, existing drill bit legs are susceptible to stress concentrations and wear induced fatigue at specific regions that also reduces the bit operational lifetime.

SUMMARY OF THE INVENTION

It is one objective of the present invention to provide a rock drill bit and in particular a rotary drill bit configured to evacuate cuttings as quickly as possible from the cutting region. It is a further objective to minimise stress and wear of the drill bit at locations close or proximate to the cutting region of the drill bit that mounts the roller cutters. Accordingly, it is a specific objective to provide a drill bit having an extended operational lifetime for example by avoiding regrinding of already cut particles and fines.

The objectives are achieved via a drill bit having a main body provided with a plurality of legs that support respectively roller cones with each leg carrying a ported boss configured with a nozzle. Each nozzle is specifically configured to create a fluid jet relative to a longitudinal axis of the drill bit that is directed radially outward from the longitudinal axis. This has been found to significantly enhance the effectiveness and efficiency of the cleaning of the cutters and/or the bottom of the hole at the cutting zone which in turn leads to a rock bit having an extended operational lifetime. According to simulations and trials of the present invention, an operational bit lifetime extension of up to 20% or even longer may be achieved.

According to a first aspect of the present invention there is provided a rock bit for blast hole drilling, comprising: a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side, and a ported boss; a plurality of roller cones, each roller cone secured to the respective bearing shaft for rotation relative thereto; a row of crushers mounted around each roller cone, wherein: each leading side and each trailing side are recessed relative to the respective shirttail, and each side has a cuttings channel formed therein, and the rock bit further comprising a nozzle disposed in each ported boss, wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle. The outward orientation of the nozzles provides more efficient cleaning of both the cutters and also the hole bottom which in turn increases the bit operational lifetime.

Preferably, each leading cuttings channel and the respective trailing cuttings channel are asymmetric. The asymmetric orientation of the respective cuttings channels is configured for controlling the evacuation of cuttings to exit the hole bottom as quickly as possible and to control the wear pattern of the bit by moving the cuttings according to a predetermined flow pathway over the bit body.

Optionally, the outward angle ranges between five and twenty-five degrees, eight to fifteen degrees, ten to thirteen degrees or between eleven to twelve degrees. Such angles have been found through simulation and testing to offer enhanced cutter and hole bottom cleaning and in turn minimise regrinding of already cut rock to avoid the creation of very abrasive fine powders and unnecessary wear of the bit.

Optionally, each leading side is concave and each trailing side is faceted. The faceted milling of the bit body is advantageous to control the wear pattern at the region of the legs by moving the cuttings in a circumferential direction towards the cuttings channel. Optionally, each leading cuttings channel has a cross-sectional shape of a circular segment, each trailing cuttings channel has a fillet, a radius of each leading cuttings channel is at least twice a radius of each trailing cuttings channel. Such a configuration is advantageous for promoting axially rearward travel of the cuttings over the bit body away from the hole bottom and to avoid recirculation of the cuttings around the bit body.

Optionally, each circular segment of the respective leadings cuttings channel may be less than one-quarter of a circle.

Optionally, each leading side further has a first bevel extending from an edge thereof adjacent to the respective shirttail to the respective leading cuttings channel, and each leading side further has a second bevel extending from the respective leading cuttings channel to an edge thereof adjacent to an adjacent other leg. The bevels are advantageous to provide a large radius for cutting evacuation and to control the cuttings flow that in turn provides control of the wear pattern at the bit legs and over the remaining bit body.

Optionally, each trailing cuttings channel further has: a first face extending from an edge of the respective trailing side adjacent to the respective shirttail to the respective fillet, and a second face extending from the fillet to a bevel, each trailing side has the respective bevel extending to either an edge thereof or to the respective ported boss.

Optionally, each first face and the respective second face has an angle therebetween ranging between eighty and one-hundred degrees.

Optionally, each leading cuttings channel has an inlet located at a lower edge of the respective leading side and an outlet located at an upper edge thereof adjacent to the respective base, and each trailing cuttings channel has an inlet offset from a lower edge of the respective trailing side and an outlet located at an upper edge thereof adjacent to the respective base.

Optionally, a longitudinal centerline of each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit, and a longitudinal centerline of each trailing cuttings channel is slightly curved extending from the inlet thereof for a short portion of the length and is then straight along the rest thereof and inclined relative to the longitudinal axis of the rock bit. Such configurations further assist the axially rearward transport of the cuttings away from the hole bottom to avoid regrinding and accelerated wear of the bit body.

Optionally, each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between ten and thirty degrees, and the straight portion of each trailing cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between two and fifteen degrees. Such configurations further assist the axially rearward transport of the cuttings away from the hole bottom to avoid regrinding and accelerated wear of the bit body.

Optionally, longitudinal centerlines of each leading and the respective trailing cuttings channels converge toward each other from the respective inlets thereof to the respective outlets thereof.

Optionally, each leg has a lubricant reservoir formed therein and a pressure compensator disposed therein. Preferably, each lubricant reservoir is located adjacent to the respective trailing cuttings channel.

In one aspect, the present rock bit comprises cuttings channels for flow optimization. In one embodiment, a rock bit is provided for blast hole drilling that includes: a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side, and a ported boss; a plurality of roller cones, each roller cone secured to the respective bearing shaft for rotation relative thereto; a row of crushers mounted around each roller cone.

Preferably, each leading cuttings channel and the respective trailing cuttings channel are asymmetric. The asymmetric orientation of the channels is effective for optimized cleaning of the hole bottom and the efficient rearward transport of cuttings to avoid regrinding which in turn reduces the forward penetration rate of the rock bit and reduces the bit operational lifetime via undesirable accelerated wear. It has been found that the cuttings channels being asymmetric in combination with the inclination of the nozzles is particularly effective for efficient cleaning of the hole bottom and the region around the drill bit. This asymmetric orientation further controls the wear pattern by providing the rearward transport of cuttings via controlled flow pathways.

Optionally, each leading side and each trailing side are recessed relative to the respective shirttail. Optionally, each side has a cuttings channel formed therein.

BRIEF DESCRIPTION OF DRAWINGS

A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIGS. 1 and 2A illustrate a rock bit having cuttings channels for flow optimization, according to one embodiment of the present disclosure.

FIG. 2B illustrates an orientation of a nozzle of the rock bit.

FIG. 3A illustrates a cutting face of the rock bit.

FIGS. 3B, 4A, and 4B illustrate the cuttings channels.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

FIGS. 1 and 2A illustrate a rock bit 1 having cuttings channels 15, 16 for flow optimization, according to one embodiment of the present disclosure. FIG. 2B illustrates an orientation of a nozzle 8 of the rock bit. FIG. 3A illustrates a cutting face of the rock bit. The rock bit 1 may include a body 2, a plurality of roller cones 3 a-c, a plurality of crushers 4 a-c, and a backflow valve 14. The roller cones 3 a-c and crushers 4 a-c may form the lower cutting face of the rock bit 1.

The body 2 may be made by attaching a plurality (one for each roller cone 3 a-c) of parts 2 a-c, such as forgings, together, such as by welding. Each part 2 a-c may have a portion of an upper coupling 5 and a lower leg 6. The body 2 may also have a dome 7 formed between the legs 6. The body 2 and the roller cones 3 a-c may each be made from a metal or alloy, such as steel. The roller cones 3 a-c may be equally spaced around the body, such as three at one hundred twenty degrees. The upper coupling 5 may be a threaded pin for connection to a drill rod (not shown). A bore may be formed through the upper coupling 5 and extend to a plenum 13 formed adjacent to the dome 7.

Each leg 6 may have a top base 6 e, an upper shoulder 6 s, a mid shirttail 6 h, a lower bearing shaft 6 b, a leading side 6 d, a trailing side 6 t, and a ported boss 6 p. Each bearing shaft 6 b may extend from the respective shirttail 6 h in a radially inclined direction toward a center of the rock bit 1. Each bearing shaft 6 b and the respective roller cone 3 a-c may have one or more pairs of aligned grooves (not shown) and each pair may form a race for receiving a set of roller bearings (not shown) or a journal bearing sleeve (not shown). One or more thrust washers (not shown) may be disposed between each bearing shaft 6 b and the respective roller cone 3 a-c. The roller or journal bearings and thrust washers may support rotation of each roller cone 3 a-c relative to the respective leg 6.

Each roller cone 3 a-c may be mounted to the respective leg 6 by a plurality of balls 9 received in a race formed by aligned grooves in each roller cone and the respective bearing shaft 6 b. The balls may be fed to each race by a ball passage formed in each leg 6 a-c and retained therein by a respective keeper (not shown) disposed in the ball passage and a respective ball plug closing the ball passage. Each ball plug may be attached or fastened to the respective leg 6.

Each leg 6 may have a lubricant reservoir formed therein and a lubricant passage (not shown) extending from the reservoir to the respective roller or journal bearings and thrust washers. The lubricant may be retained within each leg 6 by one or more seals (not shown) disposed in respective one or more glands (not shown) formed in an inner surface of the respective roller cone 3 a-c, thereby preventing leakage of lubricant into the blast hole (not shown). A pressure compensator 10 may be disposed in each reservoir for regulating lubricant pressure therein to be slightly greater than bottomhole pressure.

Each roller cone 3 a-c may have a plurality of lands formed therein, such as a heel land, a gage land, one or more inner lands, and a nose land. A row of gage crushers 4 a may be mounted around each cone 3 a-c at the respective gage land. A row of first inner crushers 4 b may be mounted around each cone 3 at a respective first one of the inner lands. A row of second inner crushers 4 b may be mounted around each cone 3 a-c at a respective second one of the inner lands. One or more nose crushers 4 c may be mounted on each cone 3 a-c at the respective nose land. Each crusher 4 a-c may be an insert mounted in a respective socket formed in the respective roller cone 3 a-c by an interference fit. Each crusher 4 a-c may be made from a cermet, such as a cemented carbide, and may have a cylindrical or conical portion mounted in the respective roller cone 3 a-c and a conical, chisel, or a proprietary shaped portion protruding from a respective land of the respective roller cone. The rows of inner crushers 4 b and nose crushers 4 c may be offset relative to one another to obtain a complete cutting profile.

A first row of heel protectors 11 a may be mounted around each roller cone 3 a-c at the respective heel land. A second row of heel protectors 11 a may be mounted around each roller cone 3 a-c between the respective heel land and the respective gage land. Each heel protector 11 a may be an insert mounted in a respective socket formed in the respective roller cone 3 a-c by an interference fit. The shirttail 6 h and the shoulder 6 s of each leg 6 may also be protected from erosion and/or abrasion by respective protectors 11 b mounted therealong. Each leg protector 11 b may be an insert mounted in a respective socket formed in the respective leg portion by an interference fit. Each protector 11 a,b may be made from a cermet, such as a cemented carbide, and may have a cylindrical or conical portion mounted in the respective socket and a dome shaped portion protruding from the respective socket.

Alternatively, the crushers 4 a-c and/or protectors 11 a,b may be capped with polycrystalline diamond (PCD). Alternatively, each crusher 4 a-c may be a hardfaced milled tooth.

Each ported boss 6 p may be in fluid communication with the plenum 13 via a respective port formed in the upper coupling 5 and may have one of the nozzles 8 fastened therein for discharging for discharging drilling fluid, such as air, into interfaces between the roller cones 3 a-c. Each ported boss 6 p may be located adjacent to the trailing side 6 t of the respective leg 6. The port of each boss 6 and the respective nozzle 8 therein may be inclined relative to a longitudinal axis of the rock bit 1 by an outward angle 12 such that the stream of drilling fluid discharged by the respective nozzle is aimed toward the interface between adjacent rows of gage crushers 4 a. The outward angle 12 may range between five and twenty-five degrees. Each nozzle 8 may be made from an erosion resistant material, such as a ceramic or cermet, such as a cemented carbide.

The backflow valve 14 may be fastened to the body 2 in the bore of the coupling 5. The backflow valve 14 may include a seat, a valve member, and a biasing member. The biasing member may operate to bias the valve member toward a closed position. The valve member may be moved from the closed position to an open position by injection of the drilling fluid down the bore of the bit body 2 and may close if flow is ceased or may close to block upward flow.

FIGS. 3B, 4A, and 4B illustrate the cuttings channels 15, 16. While only the part 2 a is shown, the part 2 a may be typical of the other two parts 2 b,c. Each top base 6 e may be a cylindrical segment having an outer base diameter (when considered cumulatively with the other top bases). The outer base diameter may be a minimum outer diameter of the legs 6. An outer profile of the legs 6 may increase significantly along the shoulders 6 s from the bases 6 e to the shirttails 6 h and then gradually along the shirttails from the shoulders to the bearing shafts 6 b. An outer profile of the legs 6 may also increase significantly from the bases 6 e to nozzle ends of the ported bosses 6 p. The leading side 6 d and the trailing side 6 t may be recessed relative to the shirttail 6 h, thereby serving as passages for cuttings transport during blast hole drilling. The trailing side 6 t may also be recessed relative to the ported boss 6 p.

The leading side 6 d may be concave and include the leading cuttings channel 15. The leading side 6 d may further include a first bevel 17 a extending from an edge of the leading side adjacent to the shirttail 6 h to the leading cuttings channel 15. The leading cuttings channel 15 may have a cross-sectional shape of a circular segment with a radius 15 r. The circular segment may be less than one-quarter of a circle. The leading side 6 d may further include a second bevel 17 b extending from the leading cuttings channel 15 to an edge of the leading side adjacent to the leg 2 c.

The leading cuttings channel 15 may have an inlet 15 n located at a lower edge of the leading side 6 d and an outlet 15 o located at an upper edge of the leading side adjacent to the base 6 e. A longitudinal centerline (not shown) of the leading cuttings channel 15 may be inclined relative to the longitudinal axis of the rock bit 1, such as by an angle ranging between ten and thirty degrees.

The trailing side 6 t may be faceted and include the trailing cuttings channel 16. The trailing cuttings channel 16 may include a first face 16 a, a fillet 16 f, and a second face 16 b. The first face 16 a may extend from an edge of the trailing side 6 t adjacent to the shirttail 6 h to the fillet 16 f. The fillet 16 f may have a radius 16 r. The leading radius 15 r may be greater than the trailing radius 16 r, such as at least twice that of the trailing radius. The second face 16 b may extend from the fillet 16 f to a bevel 18. The first 16 a and second 16 b faces may be perpendicular or essentially perpendicular, such as having an angle therebetween ranging between eighty and one-hundred degrees. Depending on location along the leg 6, the bevel 18 may extend to either an edge of the trailing side 6 t or to the ported boss 6 p.

The trailing cuttings channel 16 may have an inlet 16 n offset from a lower edge of the trailing side 6 t and an outlet 16 o located at an upper edge of the trailing side adjacent to the base 6 e. A longitudinal centerline of the trailing cuttings channel 16 may be slightly curved extending from the inlet 16 n thereof for a short portion of the length and may then be straight along the rest thereof and inclined relative to the longitudinal axis of the rock bit 1, such as at an angle ranging between two and fifteen degrees. The pressure compensator 10 and lubricant reservoir may be located in a portion of the trailing side 6 t delineated by the bevel 18. The pressure compensator 10 and lubricant reservoir may also be located adjacent to the trailing cuttings channel 16.

The longitudinal centerlines of the cuttings channels 15, 16 may converge toward each other from the inlets 15 n,16 n thereof to the outlets 15 o,16 o thereof. The cuttings channels 15, 16 may be asymmetric.

Advantageously, the recessed sides 6 d,t (having the respective cuttings channels 15, 16) and the oriented nozzles 8 may prevent or minimize the regrinding of cuttings, thereby extending the service life of the rock bit 1.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow. 

1. A rock bit for blast hole drilling, comprising: a body having a coupling formed at an upper end thereof and a plurality of lower legs, each leg having a top base, an upper shoulder, a mid shirttail, a lower bearing shaft, a leading side, a trailing side, and a ported boss; a plurality of roller cones, each roller cone secured to the respective bearing shaft for rotation relative thereto; a row of crushers mounted around each roller cone, wherein each leading side and each trailing side are recessed relative to the respective shirttail, and each side has a cuttings channel formed therein; and a nozzle disposed in each ported boss, wherein each nozzle is inclined relative to a longitudinal axis of the rock bit by an outward angle.
 2. The rock bit of claim 1, wherein each leading cuttings channel and the respective trailing cuttings channel are asymmetric.
 3. The rock bit of claim 1, wherein each outward angle ranges between five and twenty-five degrees.
 4. The rock bit as claimed in claim 3, wherein the outward angle is between eight to fifteen degrees.
 5. The rock bit as claimed in claim 3, wherein the outward angle is between ten to thirteen degrees or between eleven to twelve degrees.
 6. The rock bit of claim 1, wherein each leading side is concave and each trailing side is faceted.
 7. The rock bit of claim 6, wherein each leading cuttings channel has a cross-sectional shape of a circular segment, each trailing cuttings channel has a fillet, and a radius of each leading cuttings channel is at least twice a radius of each trailing cuttings channel.
 8. The rock bit of claim 7, wherein each leading side further has a first bevel extending from an edge thereof adjacent to the respective shirttail to the respective leading cuttings channel, and each leading side further has a second bevel extending from the respective leading cuttings channel to an edge thereof adjacent to an adjacent other leg.
 9. The rock bit of claim 7, wherein each trailing cuttings channel further has a first face extending from an edge of the respective trailing side adjacent to the respective shirttail to the respective fillet, and a second face extending from the fillet to a bevel, each trailing side having a respective bevel extending to either an edge thereof or to the respective ported boss.
 10. The rock bit of claim 1, wherein each leading cuttings channel has an inlet located at a lower edge of the respective leading side and an outlet located at an upper edge thereof adjacent to the respective base, and each trailing cuttings channel has an inlet offset from a lower edge of the respective trailing side and an outlet located at an upper edge thereof adjacent to the respective base.
 11. The rock bit of claim 10, wherein a longitudinal centerline of each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit, and a longitudinal centerline of each trailing cuttings channel is slightly curved extending from the inlet thereof for a short portion of the length and is then straight along the rest thereof and inclined relative to the longitudinal axis of the rock bit.
 12. The rock bit of claim 11, wherein each leading cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between ten and thirty degrees, and the straight portion of each trailing cuttings channel is inclined relative to the longitudinal axis of the rock bit at an angle ranging between two and fifteen degrees.
 13. The rock bit of claim 10, wherein longitudinal centerlines of each leading and the respective trailing cuttings channels converge toward each other from the respective inlets thereof to the respective outlets thereof.
 14. The rock bit of claim 1, wherein each leg has a lubricant reservoir formed therein and a pressure compensator disposed therein.
 15. The rock bit of claim 14, wherein each lubricant reservoir is located adjacent to the respective trailing cuttings channel. 